Mark as single window app

There can only be one instace of the client running

Mark it as such in the .desktop file

This allows desktop environments to adjust their UI accordingly

Signed-off-by: Nicolas Fella <nicolas.fella@gmx.de>

mirall.desktop.in

@@ -9,6 +9,7 @@ Icon=@APPLICATION_ICON_NAME@
 Keywords=@APPLICATION_NAME@;syncing;file;sharing;
 X-GNOME-Autostart-Delay=3
 MimeType=application/vnd.@APPLICATION_EXECUTABLE@;x-scheme-handler/@APPLICATION_URI_HANDLER_SCHEME@;
+SingleMainWindow=true
 Actions=Quit;
 
 # Translations